>I have two Super Nova chuck bodies, one for use on my mini, one on my big lathe. The problem I'm having is ocurring with both chucks (one is less than a year old).
Here's the problem, noticed first when turning bottlestoppers. Using pin jaws to hold the wood dowel, I turn the blank with the tailstock up against the blank. When I remove the tailstock to finish the tip of the blank, there is run-out or wobble at the very end. I get an unintended 'swirl' on my work from the tool.
I also get this when I use the 4 prong spur insert that you can use in the jaws. I noticed when the insert is in place - no wood yet - there is a slight wobble at the end of drive spur point.
I have tried reseating the jaws, on either chuck, and that doesn't solve the problem. This happens with the pin jaws and the standard jaws.
Have I overtightened them and warped them out of shape? Has anyone else experienced a similar problem.
I would check that the inserts for both chucks are absolutely straight. With the machine off (and unplugged) put either a dial gauge or some kind of straight edge on the bed and against the face of your chuck. Slowly turn by hand and watch for any runout there. You could take the jaws off for that step. If there is (wobble) there then that could be your problem.
I had a similar problem with a Oneway chuck. I took the adapter off, washed all parts in WD40, reassembled it all and the problem went away.
You can also get that problem if the tailstock is slightly out of line. Because you can see movement at the headstock end, I wouldn't think that was your problem.
>I would look first at the seating of the insert to the chuck and then the fit of the insert to the spindle. I needed a precesion ground spacer for my spindle because the insert was not bottoming on the spindle shoulder.
>I will chime in here simply because I have done a lot of very small finials and such using my Super Nova with pin jaws prior to my purchase of a Beall Collet chuck. I have used both the Supper Nova and the Nova Midi and have not experienced the problems that you are describing as being a chuck problem. From your description though it would seem that the problem appears after the removal of the tailstock so I am wondering if you have checked the alignment between your head and tail stock.
When I first started using my Grizzly lathe I experienced similar problems and I found that the tailstock was not lining up to the headstock and needed adjustment then I also found that I was over tightening the tailstock and this was causing the piece I was working on to bow from the force I was applying.
>I'm heading in the same direction as George on this. My guess is one of two things. Either tailstock misalignment is allowing you to turn a true object while slightly off center of the bed, and when the tailstock is removed the piece realigns itself and you suddenly find it off center.
Or, the tailstock restrains the natural wood movement that occurs when you alter the dimensions of a cyclinder, and when you release the tailstock, and the restraint, it moves out of round.
Since it happens regularly, I'd bet on tailstock alignment.
>There may be nothing wrong with your chuck. Chucks need clearances between their moving parts. Some chucks have more clearance than others, and some are a downright sloppy fit.
Chucks have 2 and sometimes 3 places where the wrench can be used. Use all of them. Never tighted the chuck from just one location. When you use the wrench just one (1) time, all of the clearance between the scroll plate and the base jaws is pulled to one side. Rotate the chuck a half-turn and tighten again to pull everything back to center. You should notice that this one will be a little loose. Go around the chuck two (2) times until all have the same torque, and you will have done the best you can at bringing the jaws to the center of the chuck.
The sequence for attaching the face-jaws to the base-jaws should always be to tighten all screws just "barely finger tight"; then bring the jaws together to just snug, not tight, while going around the chuck as described above. Then tighten the screws with the wrench. You now have the jaws centered with each other and with the chuck body. You may have to run a file along the edges of the jaws to remove burrs so they will snug up with each other. If there is still runout, there is a misalighment somewhere else in the manufacture of the chuck or the jaws.
The 3rd possible place to get runout is in how the wood is oriented to the jaws. Look at the chucking spigot or recess, and observe how the grain runs across it. The only points where all jaws will have the same orientation with the grain, and see the same resistance to compression of the wood, is at the 45-degree locations. All other orientation will have the jaws gripping wood with varying resistance to compression. The 45-degree orientation is automatic if you always grip something in the chuck with the grain running parallel to a separation line between the jaws.
Most of the time, any diameter within the range of the jaws will be OK, but there will be times when it isn't. All chuck jaws work best when the diameter of the spigot or recess is the same as the "true diameter" of the jaws. This insures that there are equal compression in the wood at at every jaw all the way around the wood being held. There was a time when we did this out of necessity because the early chucks had very little movement. I have one that has less than a 1/2" range. Modern chucks, with their large diameter range, have made us sloppy.
Lastly, any chuck will have some orientation of the face-jaws that runs better than others. Move the jaws around to different locations on the base jaws until you find an orientation that runs better than the others. Then, Mark the jaws so they can always be returned to these same locations. Don't pay any attention to any numbering that is already on the jaws because it may not mean anything (see below).
Develop these good habits before blaming the manufacturer.
On that topic......
The problems of eccentricity are often with the face jaws and how they are manufacturered. The face jaws are turned in a metal lathe and then cut into the 4 jaws with a slitting saw on a milling machine. Within normal machining tolerances, there is always the possibility that these separation lines will not be exactly across the center of the jaws, or they may not be at right angles to each other. Sometimes the error is greater than normal machining tolerances, and "normal" will have a different meaning with different manufacturers.
What happens next will determine how accurate the jaws will run when they are attached to a chuck in the lathe. If the 4 jaws are marked and kept together as a set, they can always be put back together in their original round shape. However, if the jaws are all thrown together not kept together as a set, it will be by accident that any 4 jaws can be selected and have them places back to their original roundness. How close they come will depend on their machining tolerances, and in particular how accurately they were cut apart.
There was a time when it was a good bet that any jaws in the same box and marked as 1, 2, 3, and 4, were a matched set. Those that weren't, weren't a set. That is no longer true, because mismatched jaws can be marked as a "set" to give the illusion of quality.
Keeping everything together as a "matched set" is standard practice for making the jaws for a machine shop chuck. Most manufactures don't think it necessary for a woodturning chuck. Most of the time they are right. But when we need accuracy and can't get it, we have to disagree with them.
The manufacturer of jaws for the woodturning chuck has two (2) choices. They can keep the jaws together as a "set" during their manufacture and marking them as such, or they can have machining tolerances such that all jaws are interchangeable. Some do both, some do one or the other, and some do neither and sometimes mark them to think that they did. It will take using several from each manufacturer to determine who does what and how often. The greater degree of care costs money, no matter where they are made. We can't buy a cheap chuck with cheap jaws and expect machine shop accuracy.
>I have a PSI chuck, and use it only for small work until I can afford another..I have a talon I use for all other, but the psi chuck doesn't seat all the way down onto the spindle of the lathe, and I spacer is what is needed...where can one get a spacer for a 1x8 tpi spindle?...the psi chuck has to be positioned just right in order to use it and worried it will damage my threads in time...tks..Dennis
>I have a similar problem with my Super Nova chuck, although it is more pronounced with the standard jaws than the pin jaws. I have checked the tail stock alignment and can't detect any mismatch there. When I round a piece between centers, then put a tenon on each end, e.g. for a box or pepper mill, then put the piece in the Super Nova I get very significant runout. The runout is the same for both tenons. I have tried many of the checks Russ Fairfield mentioned, but not all of them - I will do it all again.
That it is a problem with the chuch/jaws/insert was confirmed when I borrowed a Vicmarc - no detectable runout at 15 inches when I chucked the spindle to turn a long stemmed goblet. Hopefully that heavy box that arrived from Craft Supplies addressed to my wife will solve the problem around the end of the month:-)
>The best spacer for a chuck is the one that you make.
Chuck up a piece of wood with the grain on the centerline of the lathe, turn it to outside diameter, and drill a 1" hole. Any wood will do, but Oak would be the best choice.
Then face the end and cut to length with the parting tool, making them as close to square and flat as you can. Don't worry about error or rough surface. Do the best you can, and use the spacer as it was cut. Do not sand these cut ends of the spacer.
I would say Russ pretty well covered the whole gambit and I agree with him, there is one addition that I think should be looked at, the fit of the chuck onto the spindle, a chuck should have a slip fit on the shaft and a solid fit to the face it seats to, the threads have ( normally ) to much clearance to centre the chuck properly, one more thing is, if the chuck gets knocked around over time, there might be a very slight burr or flat spot on the chuck's shoulder or spindle face, 2 or 3 thou on the 1" shaft face levers to 10-15 thou over the 4 to 5" in length and that makes for 20 to 30 thou total run out, and what was almost not noticeable you now would call a wobble .
So I would say, have a real good look at the mating surfaces and make absolutely sure they are in good conditioning.
>Thanks to everyone who responded, especially Russ. A thorough answer, as one has come to expect from Russ.
I've tried a couple of the things that were mentioned, and have the Oneway alignment kit that I got with the outboard attachment to line up the riser block/tailstock. I will try that, although I question whether it's the tail stock. Both sets of jaws have the same problem. One is used exclusively on my Oneway, the other exclusively on my Jet Mini.
>Donna do you have access to a other chuck, like a oneway chuck, if you do not have the wobble with a different chuck, you can almost surely rule out the lineup as the cause.
Yes, I do have another chuck, the Vicmarc, with several jaws. I have not noticed any runout when using this chuck, so, I'm thinking more along the lines that the Nova chuck body needs to be cleaned out, etc. All the things that Russ suggested.
>I would like to point out that modern chucks use a scroll for adjusting all jaws simultaniously. What does happen when you tighten the chuck is that the wood fibres get compressed by the jaws. Initially they offer resistance and you think it is tight. While you move on to the next socket with your key, the wood fibres give a bit due to the clamping pressure on them. Then when you tighten the second time, you actually take up that slack. The pressure on the wood fibres is again at the max point that you can physically tighten the chuck. If you move to the next socket with your wrench the whole process repeats itself. Therefore it creates the impression that you tightened the chuck more by using the different sockets.....in fact if you paused on the same one for a bit you would find that you could screw it up quite a few times, each with a pause inbetween.
In modern scroll chucks the scroll being a single piece, it does not make any difference from which 1 point you tighten with your key, as the whole scroll moves regardless of where you tighten from. However the fibres give after the pressure has been on for a while, hence the illusion.
Dismantle a modern scroll chuck and you'll see exactly what I am talking about. I have verified this with a scroll chuck manufacturer and also with a few mechanical engineers where we actually inspected some modern scroll chucks. I use the word modern because drill chucks etc were differently designed in years way back.
Enjoy your turning........tighten your chuck a few times in succession.... no matter which hole
